The present invention relates to disposable cigarette filters of the type generally illustrated in U.S. Pat. Nos. 3,375,920 and 3,137,303. Disposable cigarette filters of this type are made with an absorbent fibrous filter impregnated with a fluid such as water. Such filters must be designed for automatic, efficient and inexpensive manufacture. These filters must also be designed for ease and safety in use. To attain these and other ends, filters of this type have been made with insert metal sleeves designed to be inserted in the cigarette receiving end of a plastic casing. These metal sleeves are intended to be used as heat sinks as well as means for engaging the cigarette which is inserted in the sleeve. The sleeves which have been used heretofore do provide adequate heat sinks. However, these sleeves do not always satisfactorily secure an inserted cigarette.
Cigarettes frequently accidentally fall from the sleeve when the filter is in use. These inadvertencies are both annoying to the user and hazardous; it is therefore desirable to eliminate them as far as possible. The sleeves which have been in use heretofore do not adequately secure the cigarette from accidental dislodgment at all times because of the diameter variation that occurs from cigarette to cigarette.
Cigarette filters of this type which contain a charge of water or the like must be prepackaged in such a manner as to seal the ends of the filter against evaporation. Several systems have been in use for this purpose. For example, as shown in U.S. Pat. No. 3,375,920 the mouthpiece end is normally sealed by dipping it in a liquid plastic which then solidifies into a tearable film. Other means have been used which include a twist off key or plug which is integrally formed with the cigarette casing and which is adapted to be twisted off to expose the mouthpiece opening. Both of these systems have limitations. In the case of the twist off means, the twist off element is frequently damaged and knocked off during the processing and fabrication of the filter. Since these filters are made on automatic machinery, a complete filter with a defective closure at the mouthpiece end is often completely fabricated before the defect is noted. Such defective filters are commercially useless in the absence of some simple means for effecting a closure.